Informix Vs Sql Server

We are currently investigating two products that are offering a Electronic Medical Record solution for our company. The two products have database servers. One resides on Informix and the other on Sql Server.

We are not sure if one is better than the other. I am asking the experts to tell me what you would choose and why. We are concerned about Informix not being supported in a year or two but yet is microsoft's product the right choice. Is there any difference in performance. We will have about 200 users hitting the database concurrently with a business critical application.

Personally I wouldn't worry too much about the database in relation to the numbers of users -- the application and hardware are the two major factors -- the database will undoubtedly cope (these are both enterprise RDBMS's) as long as the application is well written (and I assume your potential vendors know what they're doing) and the database is given sufficient hardware / bandwidth given your user base (and again this should be relatively straight-forward to define -- might be harder to pay for).

The decider for me (in relation to your question) is the database software and this is won hands-down by Microsoft for the following reasons:
-Availability of development / support skills.
-Level of future development.
-Functionality, both core and extended (i.e. the availabilty of third party tools, the opportunities of Reporting Services etc.)
-No-one every got fired for buying Microsoft!

However, I wouldn't use this to decide which of your applications to go with (Informix will be around for the long term and if not your vendor will need to move platform) -- only if the applications tie on all other factors should you consider this as a selection criteria.

One vendor stated that the reason they use Informix is because it is the best solution for the Unix os which they use for its high transaction abilities and in which Microsoft doesn't really compare. Does this argument hold merit??

Yes -- I certainly 'prefer' a UNIX hosted database (UNIX tends to be a 'cleaner' host with a more obvious relationship between processes and applications and potentially a lack of the bloatware that Microsoft suffers from). However, (much as I hate to say it) Microsoft is getting better at this sort of thing -- I understand that w2003 is a more resiliant environment than previous incarnations of windows on the server....

Given current server technologies and the move toward more smaller, flexible machines in the server cluster / farm / grid (call it what you will) the whole argument between UNIX / Microsoft servers gets clouded by issues such as load-balancing, scalability, expandibility etc....

...we come back to the earlier points -- Microsoft skills are generally easier to come-by and potentially cheaper than those associated with other platforms.

So, in summary, the argument for UNIX does hold water, but there are other factors that have bearing...

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